The present invention relates to a stencil disposal unit and stencil disposal method, and more particularly to a stencil disposal unit and stencil disposal method in which a used stencil wound around the outer periphery of a printing drum of a rotary stencil printing machine is transported to a stencil disposal container or the like and then disposed.
Upon an investigation by the inventors of the present invention, a stencil disposal unit provided in a rotary stencil printing machine is envisioned, such as shown in FIG. 8, in which the stencil disposal unit 138 automatically disposes of a used stencil from a printing drum.
The stencil disposal unit 138 is disposed in proximity to the periphery of a printing drum 112, and minimally has a pair of stencil disposal rollers 139, which are in mutual contact and which rotate in mutually opposite directions. The stencil sheet M is fed in between the stencil disposal rollers 139 and transported and recovered in a stencil disposal container 140 to the rear thereof.
In this rotary stencil printing machine the prepared stencil sheet M is automatically fed to and wound around the printing drum 112.
Specifically, as shown in FIG. 8, after a stencil sheet M is pulled out from a stencil sheet roll and, and a stencil is made from the stencil sheet M using a thermal printing head 107, it is transported to the printing drum 112. After transport to the printing drum 112, the end part of the stencil sheet M is grabbed by the clamping plate 119 at the printing drum 112, and wound around the outer periphery of the printing drum 112 by rotation of the printing drum 112. When the fixing of the stencil sheet M to the printing drum 112 is completed, a cutter unit 111 cuts the stencil sheet M.
The stencil sheet M is formed by a thermoplastic resin film, such as a polyethylene terephthalate film, a vinylidene chloride film, a polyester film, or a polypropylene film or the like, to which an ink permeable porous sheet (porous tissue carrier), made of a natural fiber, a chemical fiber, a synthetic fiber, or a thin paper, non-woven cloth, silk gauze or the like that is a mixture thereof is adhered, thereby forming a thermally sensitive stencil sheet. For a rolled stencil sheet M such as shown in FIG. 8, the ink permeable porous sheet is disposed on the outside surface. When printing is done, the ink permeable porous sheet makes contact with the outer surface of the printing drum 112.
When printing, the printing drum 112 is caused to rotate in the counterclockwise direction as shown in FIG. 8, the print paper (not shown in the drawing) being fed between the printing drum 112 and a pressure means (not shown in the drawing), which presses the print paper up against the image part of the stencil sheet M attached to the printing drum 112. By doing this, ink fed by an ink feeding means (not shown in the drawing)within the printing drum 112 passes through an ink-permeable part on the outer wall of the printing drum 112, and is transferred to the print paper via the perforation parts of the stencil sheet M so as to form an image thereon.
When the printing is completed, the disposal operation is performed by the stencil disposal unit 138. When disposing the stencil sheet M, as shown in FIG. 9, a mechanism not shown in the drawing releases the grip of the clamping plate 119 on the stencil sheet M, thereby freeing up the end part of the stencil sheet M that had been held. The printing drum 112 is then caused to rotate in the counterclockwise direction shown in FIG. 8, so that the freed-up end part of the stencil sheet M is fed between the pair of stencil disposal rollers 139, causing disposal of the stencil sheet M.
According to an investigation by the inventors, however, with the stencil disposal unit 138, the freed-up end part of the stencil sheet M that had been held by the clamping plate 119 has a tendency to curl, as shown in FIG. 9.
If the stencil sheet M curls, this curl can cause the end to miss the space between the pair of stencil disposal rollers 139, so that it is not transported into the stencil disposal container 140. Additionally, because of the curving tendency of the rolled stencil sheet M, the expansion of the ink permeable porous sheet making up the stencil sheet M due to humidity in the air, and the influence of temperature and static electricity, the curl of the end part of the stencil sheet M often tends to be in a direction away from the printing drum 112. By the rotation of the printing drum 112 during stencil disposal, there is resistance that urges the curl to move further away from the printing drum 112, thereby aggravating the problem of curl.
For this reason, it can be envisioned that, in the stencil disposal unit 138, as shown in FIG. 11, an endless guide belt 145 is wound between a stencil disposal roller 139a, which, of the pair of stencil disposal rollers 139, is farther from the printing drum 112, and a pulley 146 is disposed above the clamping plate 119, so as to guide a curled end of the stencil sheet M to between the pair of stencil disposal rollers 139. If this is done, the guide belt 145 is rotationally driven by the rotation of the stencil disposal rollers 139.
Another arrangement that can be envisioned is, as shown in FIG. 11, to provide an air blower 160 that applies pressure to the printing drum 112 side of the end part of the stencil sheet M to be curled, the air flow from the air blower 160 guiding the end part of the stencil sheet M to between the pair of stencil disposal rollers 139.
It is also possible to combine elements of the guide belt 145 and the air blower 160.
However, as the investigation by the inventors progressed further it was understood that, in the configuration in which a guide belt 145 is provided in the stencil disposal unit 138, the position at which the guide belt 145 is provided is very close to the clamping plate 119, so that it interferes with the swinging range of the clamping plate 119.
For this reason, when the clamping plate 119 is caused to swing, it is necessary to have an added moving mechanism such that the pulley 146 onto which the guide belt 145 is wound is moved about the stencil disposal rollers 139 as a center, so that the guide belt 145 does not come into contact with the clamping plate 119.
While it can be envisioned that the stencil disposal unit 138 having the guide belt 145 be positioned at a distance from the clamping plate 119, thereby eliminating the need for the added moving mechanism, when the stencil disposal unit 138 is moved away from the clamping plate 119, because the angle through which the printing drum 112 is turned after the clamping plate 119 is released becomes larger, the rotation of the printing drum 112 as noted above results in a large resistance that urges the curl to move away from the printing drum 112, so that it is not possible to establish the position of the end part thereof, leading to the problem of missed disposal operation.
If an air blower 160 is used, although this does not involve the swinging range of the clamping plate 119, another moving mechanism for the motor required by the air blower 160 is still required. Additionally, making the air blower 160 itself small will reduce the air output, making it necessary to bring this device close to the clamping plate 119.
Thus, in the investigation conducted by the inventors as to the stencil disposal unit 138, it was understood that the adopting of a configuration for the purpose of preventing faulty disposal of a used stencil was limited in terms of the positional relationship with respect to the clamping plate 119, making it difficult to achieve a suitable configuration.
The printing drum 112 is configuration to enable removal in the axial direction for the purpose of maintenance inspections or the like. In this type of configuration, if the clamping plate 119 and the stencil disposal unit 138 are in mutual proximity, when the printing drum 112 is pulled out, there is a risk that contact by the printing drum 112 will cause the clamping plate 119 to come into contact with the guide belt 146, the air blower 160 or the like of the stencil disposal unit 138.
Accordingly, the present invention was made by the above mentioned studies and has an object to provide a stencil disposal unit and stencil disposal method that substantially omits a restriction on an arrangement of structural elements due to a configuration of a printing drum, occurrence of curl of a stencil sheet or the like, and also performs disposal operation of the stencil sheet in stable and with a simple structure not required an additional mechanism such as a movable mechanism.
In accordance with the present invention, a stencil disposal unit disposing a stencil sheet an end part of which is clamped at and wound onto a printing drum of a rotary stencil printing machine having a rotational drive mechanism capable of causing the printing drum to rotate in a winding direction with respect to an end part of a stencil sheet released from a clamp and in a reverse direction opposite to the winding direction, comprises: a pair of stencil disposal rollers arranged in an area around a periphery of the printing drum and rotatable respectively in opposite directions in mutual contact with each other, thereby pulling in the end part of the stencil sheet so as to transport the stencil sheet to a predetermined disposal position. Here, by rotating the printing drum through a predetermined angle in the winding direction, the end part of the stencil sheet is guided to a pull-in position at which the stencil sheet is to be pulled in, and the printing drum is rotated in the reverse direction, as the stencil sheet is pulled in at the pull-in position by the pair of disposal rollers.
Beside, in another aspect of the present invention, a stencil disposal method disposing a stencil sheet an end part of which is clamped at and wound around a printing drum of a rotary stencil printing machine, comprises: releasing the end part of the stencil sheet from a clamp; causing the printing drum to rotate in a winding direction with respect to the end part of the stencil sheet released from the clamp, so as to guide the end part of the stencil sheet to a pull-in position; and causing the printing drum to rotate in a reverse direction opposite to the winding direction, as pulling in the end part of the stencil sheet.